1. Field of the Invention
The invention relates generally to an electrode having a rigidly mounted electrode element adapted for use with an endoscope for tissue resection, coagulation, and ablation and more particularly relates to an electrode having a shaped conductive core electrode member having a sharp leading cutting edge for use in performing procedures, such as, for example, in the genitourinary tract on soft tissue, including bladder and prostate, for BPH procedures, for hemostasis, incision, excision and ablation or in performing other surgical procedures requiring removal or ablation of tissue.
2. Description of the Prior Art
Use of resectoscopes to treat tissue in the genitourinary tract is well known. Typical of such resectoscopes are the devices disclosed in U.S. Pat. Nos. 5,151,101 and 4,955,884.
Resectoscopes used for transurethral resection of the prostate (TURP) have four elements, a resectoscope sheath, sometimes referred to as a sheath or an outer sheath, a working element, an electrode and a telescope. The electrodes are operatively connected to a working element and a telescope is slideably inserted through the working element and into position along side of the electrode. Certain electrodes include an electrode stabilizer which is adapted to receive the telescope. The so assembled working element, telescope and electrode are removably inserted into the sheath to perform a procedure.
In a typical urological procedure, the sheath with its obturator, is passed through the urethra to the vicinity of the prostate and/or bladder neck. The obturator is then removed and the resectoscope working element with a telescope and electrode assembled thereto is inserted into the sheath. The electrode, which is also known as a resectoscope electrode, is typically in the form of a cutting loop located at the distal end of an electrode lead member.
An electrosurgical current, which may be either a coagulation current, a cutting current or some blend thereof is applied to the cutting loop. The energized cutting loop is moved through the prostatic tissue and cuts the tissue being treated. The cutting loop can also be used to coagulate the severed vessels in the tissue. In urological procedures, under water, the peak voltage of the electrosurgical cutting currents are typically in the range of 200 volts to about 500 volts at a power level of between about 100 watts to about 300 watts.
A resectoscope electrode having a stabilized cutting loop for a resectoscope is described in U.S. Pat. No. 4,917,082.
The resectoscope electrode described in U.S. Pat. No. 4,917,082 is adapted for use with a urological endoscope or resectoscope. The electrode comprises an electrode lead, an electrode end and an electrode stabilizer. U.S. Pat. No. 4,917,082 discloses that the electrode may take the form of a coagulating electrode, knife electrode, retrograde knife electrode, punctate electrode or roller electrode having a smooth exterior surface.
Continuous flow resectoscopes which utilize a cutting loop electrode for urological procedures are well known in the art and an example of a continuous flow resectoscope is disclosed in U.S. Pat. No. 3,835,842.
An article entitled "THE USE OF THE RESECTOSCOPE IN GYNECOLOGY" by Richard A. Auhll which appeared at pages 91 through 99 of the Oct. 11, 1990 issue of Biomedical Business International (the "Auhll Reference") disclosed the use of a uterine resectoscope system in the form of a continuous flow resectoscope using an electrosurgical electrode for performing intrauterine procedures.
The Auhll Reference discussed three electrode structures, namely: (1) an electrosurgical cutting loop to treat fibroid tissues; (2) a roller ball having a smooth exterior surface for endometrial ablation (which is cauterization of the endometrium); and (3) electrosurgical needle to cut through and destroy tissue producing intrauterine synechia. In gynecological procedures, the voltage of the electrosurgical cutting currents are typically in the range of 200 volts to about 400 volts at a power level of between 60 watts and 200 watts.
In order to increase the efficiency of treatment of the prostate tissue generally, and the treatment of benign hypertrophy of the prostate (BPH) in particular, several new procedures and devices have been developed. These procedures and devices include the use of a Nd:YAG laser for the coagulation and vaporization of prostate tissue generally referred to as abdominal tissue. In order to use Nd:YAG lasers for treatment of BPH, optical fibers capable of deflecting a Nd:YAG laser energy beam about 70.degree. to about 90.degree. to the axis of the optical fiber (generally known as side-firing fibers) have been developed.
Use of a direct contact laser fiber is discussed in an article entitled "TRANSURETHRAL EVAPORIZATION OF PROSTATE (TUEP) WITH Nd:YAG LASER USING A CONTACT FREE BEAM TECHNIQUE: RESULTS IN 61 PATIENTS WITH BENIGN PROSTATIC HYPERPLASIA" by Perinchery Narayan, M.D., George Fournier, M.D., R. Indudhara, M.D., R. Leidich, M.D., K. Shinohara, M.D. and Alex Ingermann, M.D. which appeared at pages 813 through 820, in the June, 1994, Volume 43, Number 6, Issue of Urology (the "Narayan et al. Reference"). The Narayan et al. Reference discusses the use of laser surgery for BPH as a promising alternative to traditional TURP. The Narayan et al Reference discloses that in prostate surgery tissue evaporization referred to as Transurethral Evaporization of Prostate Tissue ("TUEP") was achieved by holding the laser fiber in contact with the area to be treated. The TUEP was performed using an ULTRALINE Laser Fiber manufactured by Heraeus LaserSonics, Milpitas, Calif. The ULTRALINE Laser Fiber uses a 600 microns internal reflector fiber covered by a quartz glass cap that reflects the Nd:YAG beam at 80 degrees to the fiber axis. This fiber transmits a high-power density beam (spot size of 700 micron and divergence of 17 degrees, giving a power density at 60 watts to 80 watts of 16,000 to 21,000 W/cm.sup.2) 1 mm from the fiber tip. A 23 French cystoscope (CIRCON ACMI, Stamford, Conn.) equipped with an 8 French laser bridge and a continuous flow system was used for the procedure.
The results as stated in the Narayan et al. Reference was as follows:
" . . . Tissue evaporation was achieved by holding the laser fiber in contact with the area to be treated, and by dragging at a rate of 1 cm/20 seconds of laser energy delivery. At the beginning of each furrow dragging was commenced one bulling was seen indicating tissue evaporation. Dragging the fiber at a rate of 1 cm/20 seconds resulted in a furrow 5 to 7 mm deep with a 3 to 4 mm rim of coagulated tissue immediately next to it." PA1 "T.U.D (transurethral desiccation of the prostate) was first described in 1874 by Bottini. Since 1966 we have used this visually controlled exact vaporization of the prostate in over 500 men with benign hypertrophy, cancer and bladder neck disease. PA1 In the present method (T.V.P., transurethral vaporization of the prostate) a grooved ball electrode and pure electrosurgical cutting current is used to sculpt out the prostatic bed. T.V.P. has the advantage that it causes little or no bleeding, fluid absorption or electrolyte imbalance. Since the residual desiccated tissue (adequate for pathologic review) is removed at the end of the procedure, there is no slough or delayed bleeding (open vessels are closed without retraction). The patient can leave the hospital, voiding (76%) within the 23 hour observation time in most instances. A new improved scored ball loop (A.C.M.I.) to be used with a continuous flow resectoscope has become available. PA1 T.V.P. is a short procedure without sphincter damage which preserves antegrade ejaculation and has a low (2-3%) subsequent procedure rate. Our experience with the last 100 consecutive patients will be detailed." PA1 "With the wide interest shown in the relief of prostatic encroachment by the intravesical route, we offer this apparatus as the only present day means for actuating some of the electrodes used for this purpose. The splendid action of this current in a liquid medium has eliminated the hazard of failure at the current source. PA1 The method advocated by Dr. Joseph F. McCarthy, for whom this apparatus was designed, permits great flexibility and with proper technique, the entire prostatic urethra can be remodeled. PA1 The Stern Resectoscope under the able guidance of Dr. T. M. Davis has been modified for greater durability and effectiveness. Other surgical methods that have required the use of high frequency currents have been spurred to new activity. PA1 Here again the requirements have been fully and adequately met and an excess of power provided that will encourage continued research. Those engaged in this specialty are freed of the limitations imposed by generators hitherto available. PA1 In the practice of urology the McCarthy Unit provides every modality. Every purpose which requires the use of high frequency current is served; fulguration of cysts, papillomata, tumors, etc., coagulation control of bleeding, resection and treatment. PA1 The current supplied by the type 504-A unit although very efficacious in resection, shows no effect on delicate insulating materials, greatly prolonging the useful life of urological instruments and electrodes. The selective foot switch permits hemorrhage control with the same electrode used for resection, without the necessity of changing the controls on the apparatus." PA1 "The unit generates by one type of current, and the controls merely provide the means for adjusting its intensity. It has been established that the same current that shows such admirable cutting characteristics is also the most effective for coagulation. By virtue of its penetrating quality the time necessary for coagulating tumor masses or malignancies has been greatly reduced. Sections of coagulated areas show a tapering off into unaffected tissue that practically eliminates the possibility of secondary hemorrhage. Tumor masses show a remarkable shrinkage during application, proportional to their fluid content. PA1 The technique used in coagulation with this type of current is the same as used for tissue destruction and for hemorrhage control. The electrode must be placed in contact with the area to be treated before the current is turned on. After treatment the current must be off before the electrode is removed. No attempt should be made to ply the area with sparks. In following this technique there is no possibility of carbonization, and no tissue can adhere to the electrode."
Another known prior art device for treatment of prostate tissue was presented at a poster session at the Society of Minimal Invasive Therapy ("SMIT") on Nov. 5, 1993. The poster session was entitled "TRANSURETHRAL VAPORIZATION OF THE PROSTATE (T.V.P.): NEW HORIZONS" by Irving M. Bush, M.D., Edward Malters, M.D. and Jan Bush, R.N. (the "Bush et al. Reference") disclosed the use of an improved scored ball produced by CIRCON ACMI Division of Circon Corporation, assignee of the present patent application, with a continuous flow resectoscope for providing transurethral desiccation (vaporization) of the prostate.
The Bush et al Reference states as follows:
For purposes of background in electrosurgical treatment of tissue, there are three basic electrosurgical modes: (a) cutting (dissecting) where tissue is severed by a cutting electrode having a radio frequency ("R.F.") cutting current applied to the cutting electrode and the wounded tissue has a layer of coagulation of about 0.5 mm to about 1 mm beyond the cutting area; (b) fulguration where a ball electrode is positioned above the tissue to be treated and an R.F. arc coagulating current flashes from the ball electrode to the tissue to be treated coagulating the tissue; and (c) desiccation where a smooth ball electrode is held in direct contact with the tissue to be treated and a coagulating current of a selected magnitude is applied to the ball electrode vaporizing the tissue.
The first use of electrosurgical generator for prostatic resection using only an R.F. cutting current was in 1931, and the electrosurgical generator was a McCarthy Surgical Unit Type 504A sold by the Comprex Oscillator Corporation (the "McCarthy Surgical Unit"). The McCarthy Surgical Unit was a highly efficient vacuum tube generator producing sustained oscillation of high frequency.
The McCarthy Surgical Unit was capable of being used for numerous procedures including prostatic resection. The McCarthy Surgical Unit manual states the following with respect to prostatic resection:
The McCarthy Surgical Unit manual states that the McCarthy Surgical Unit can be used for coagulation as follows:
The McCarthy Surgical Unit utilized for coagulation and dissication a smooth ball shaped electrode having a 3/16 inch (4.5 mm) diameter.
The McCarthy Surgical Unit utilized a control panel having two dials. The first dial was referred to as the Range Selector (R.S.) having three ranges, a low, medium and high, each representing one third of the current output. The second dial was referred as the Current Intensity Control (C.I.C.) and provided smooth linear adjustment over each range. Thus, the Range Selector was a course adjustment and the Current Intensity Control was a fine adjustment. The only current produced by the McCarthy Surgical Unit was a cutting current. The maximum current was in the order of 2,600 milliamperes.
In the McCarthy Surgical Unit, for all operative work, dissection, coagulation, bladder fulguration, prostatic resection and the like, a plate electrode was placed under the patient and connected to an indifferent, terminal which is usually a ground terminal, to ground the patient.
In using the McCarthy Surgical Unit for prostatic resection, bleeding resulting from the removal and vaporization of tissue using high intensity cutting current was controlled by passing the same electrode over the same treated tissue area using a low intensity cutting current for providing coagulation of the treated tissue.
Typically, the resulting coagulation layer of the heated tissue had a thickness in the order of 0.5 mm to about 1 mm which appeared sufficient to stop bleeding.
The following U.S. Patents disclose apparatus having electrosurgical electrodes: U.S. Pat. No. 5,395,363; U.S. Pat. No. 4,917,082; U.S. Pat. No. 4,765,331; U.S. Pat. No. 4,532,924; U.S. Pat. No. 4,314,559; U.S. Pat. No. 4,095,601; and U.S. Pat. No. 642,849.
U.S. Pat. No. 5,395,363 discloses an apparatus for facilitating diathermy coagulation or ablation of tissue by the application of an electrical current to tissue. The apparatus is electrically connected to an electrosurgical generator and has both monopolar and bipolar embodiments. The apparatus includes a roller electrode, as the active electrode, having a plurality of discrete electrical discharge points. The plurality of discharge points is provided by diamond knurling the exterior surface of the active electrode providing a plurality of distinct points for current discharge, facilitating evenly distributed current through the tissue.
U.S. Pat. No. 4,917,082 discloses an electrode for use with urological endoscopes. The electrode comprises an electrode lead, an electrode end and an electrode stabilizer. In the preferred embodiment, the active electrode is a cutting loop used to perform transurethral resection of the prostate ("TURP"). FIG. 5E of U.S. Pat. No. 4,917,082 discloses an alternative embodiment of an electrode wherein the electrode tip 22 comprises a roller electrode having a smooth outer surface.
U.S. Pat. No. 4,765,331 discloses an electrosurgical probe for use in treatment of tissue. The probe includes an active member which is generally cylindrical and has a peripheral surface on which are mounted a plurality of electrodes. The electrodes are mounted such that an electrode of one polarity is interposed with those of the opposite polarity. The length of the electrode can be chosen to obtain desired longitudinal focusing.
U.S. Pat. No. 4,532,924 discloses a multipolar electrosurgical device and method. The device is in the form of an insulative probe body, which is sized to pass through a channel of the endoscope. The probe body is provided with electrically separate conductors which are formed of a plurality of electrodes distributed over the peripheral surface of the probe body. The electrically separate conductors are so sized in width W and spaced from each other by a distance S as to establish a ratio of W:S which enables effective bipolar orientation relative to tissue. In the preferred embodiment, a plurality of six electrodes are aligned longitudinally on the probe body and are used to form six bipolar electric fields.
U.S. Pat. No. 4,614,559 discloses a conductive non-stick electrode for use with a hemostatic tissue cutting scalpel. The scalpel has a first layer of conductive material having a textured working surface for contacting tissue and a second coating of non-stick material deposited on the first layer at least partially filling the textured surface.
U.S. Pat. No. 4,095,601 discloses an electrotherapeutic apparatus having a handle and roller shaped electrode for applying direct current voltage pulses for electrotherapeutic treatment. The roller shaped electrode has a surface that is composed of substantially pyramid shaped parts. the pyramids can either be arranged in rows oriented along surface lines or can be arranged in rows which are offset. In the arrangement where the rows of pyramids are offset, the tips of the pyramids are always located in the center between geometric tips of one pyramid to the tips of the neighboring pyramid in adjacent rows and the spacing is in the order of 6.955 mm. The pyramids do not have a geometric tip, but rather a flattened tip in the form of a square of an edge or side length amounting to 0.5 mm.
U.S. Pat. No. 642,849 discloses an electrical passage instrument which includes smooth, current applying rollers. The rollers are made of carbon and are electrically separated from each other by an insulation.